As is known, utility companies supply the public with various products including electrical power, telephone service, and natural gas. Electric utilities are continuously in the process of upgrading their distribution system infrastructure in order to be able handle the increase in electric demand and to improve the reliability of existing services. This upgrade typically involves the replacement of old wooden utility poles (in some cases 80–90 year old poles) with new wooden utility poles that are engineered for the heavier conductor loads and tensions and that provide additional clearance for the higher distribution voltages. Road widening projects may also force the electric utilities to relocate their existing facilities, even though these facilities are not necessarily in need of repair. However, both of these situations usually require the removal of existing wooden utility poles.
On a typical road-widening project, the electric utility will install a plurality of new poles and string a new conductor along the edge of the new road right of way. Once this new line is energized and electric customers are transferred over to the line, the electric utility will remove the old wires from the existing line and cut the tops of the poles off just above the communications circuits (telephone and cable TV). This procedure allows the owners of communications circuits to lift their facilities over the top of the cutoff pole and transfer their facilities to the new poles without cutting and splicing. Once the remaining facilities are relocated, the remaining portions of the poles must be removed.
It has been found that a very high percentage of new utility poles that are installed on an annual basis are actually replacement poles. For a mid-sized electric utility, this can equate to the removal and replacement of over 10,000 poles per year. As such, a safe and economic means for removing the utility poles is a necessity. Heretofore, various types of the pole pulling devices have been utilized by the electric utilities. For example, U.S. Pat. Nos. 3,163,398 and 3,173,658 disclose commercially available pole pulling devices that include hydraulic cylinders and base plate assemblies that are coupled to corresponding poles via chains that cinch the poles.
While functional for their intended purpose, these prior pole pulling devices are cumbersome to operate and have numerous disadvantages. By way of example, for rear lot line applications, prior pole-pulling devices need to be carted by hand over to the pole and then assembled. A portable hydraulic unit also needs to be carted over to the pole. Further, the chain method of cinching the pole is not very effective. The chain tends to roll and not “bite” into the outer periphery of the pole as the cylinder is extended. As a result, a wedge block must be installed (i.e., driven in with a sledge hammer) between the chain and the pole to keep the chain from slipping. Once the hydraulic cylinder is fully extended, the wedge block needs to be driven back out (again, with a sledge hammer) and the cylinder must be retracted and reattached to the pole. Because of the limited stroke of the hydraulic cylinder (typically 18–24-inches), this operation can be time consuming and labor intensive. It is also noted that on soft ground, the base on the hydraulic cylinder of a prior pole pulling device can sink into the ground during extraction, leading to more operational problems. Finally, since the hydraulic cylinder is fixed to the pole, the mechanical forces applied to the pole and to the cylinder tend to tip the pole away from the side of the pole on which the hydraulic cylinder is attached. As a result, the top of the pole may tip in an unwanted direction.
In view of the above-mentioned operational difficulties that utility line mechanics encounter when using these prior pole pulling devices, alternate methods for extracting utility poles from the earth have been developed. A preferred method used by utility line mechanics is to loosen the pole by wiggling it back and forth with a digger derrick truck. Thereafter, a derrick winch line is used to extract the pole. Digger derrick trucks are not designed for this application and this operation can lead to damage to the crane boom and turret assembly of the truck. Safety is a major concern when exceeding the design limits of the boom truck.
Other attempts have been developed to address some of the issues heretofore described. U.S. Pat. No. 4,822,006 is directed to mechanism for reducing the slippage of the chain used to pull the pole from the earth. The mechanism utilizes mechanical fingers that dig into the pole as the hydraulic cylinders are extended. However, the design of the mechanism in the '006 patent raises a number of issues. For example, the variations in pole diameters and lack of concentricity can lead to gripping problems. Further, any side load on the mechanical fingers due to the cylinder not being centered can lead to bending of the cylinder rod resulting in an expensive repair. In addition, the mechanical fingers exert substantial inward pressure on the pole prior to extraction, thereby leading to the possible crushing of the wood without ever extracting the pole. Finally, the limited stroke of the hydraulic cylinder requires multiple strokes of the cylinder to fully extract a pole, thereby requiring a substantial amount of time.
U.S. Pat. No. 4,327,534 addresses the issue of extracting the pole in a single stroke by extending the length of the hydraulic cylinder. Although this approach will work, there are still chain gripping issues and longer hydraulic cylinder rods are susceptible to damage. There are also ergonomic issues associated with installing the device next to the pole.
U.S. Pat. No. 6,641,347 utilizes a design that is mounted to a piece of mobile construction equipment. While adequate for accessible locations, the design is not well suited for rear lot line applications. One positive feature is that the large surface area of the base plate keeps the design from sinking into soft ground. Further, the design places the mechanical forces to the ground rather than the piece of construction equipment. However, since the design is mounted in a bucket, it does not allow for the bucket to be utilized to fill the hole left by the extracted pole. In addition, other problems associated with the design disclosed in the '347 patent include ergonomic issues with having to physically rotate the hydraulic cylinder into position, the limited stroke capability of the hydraulic cylinder, chain slippage issues and the fact that the utility pole has a tendency to tip away as the pole is extracted.
Therefore, it is a primary object and feature of the present invention to provide a pole pulling device that will safely and efficiently extract a utility pole from the earth.
It is a further object and feature of the present invention to provide a pole pulling device that minimizes the ergonomic impact to the machine operator.
It is a still further object and feature of the present invention to provide a pole pulling device that has the ability to be mounted on a small compact utility tractor that can be used to transport the pole pulling apparatus and that utilizes the tractor as a hydraulic power source.
It is a still further object and feature of the present invention to provide a pole pulling device that incorporates a means to lay the utility pole down on the ground after extraction without the use of a digger derrick truck.
It is a still further object and feature of the present invention to provide a pole pulling device that is simple to operate and inexpensive to manufacture.